lodashのcloneを用いた実装

gistfile1.js

var _ = require('lodash');

function iPush(arr, val) {
  var arr2 = _.clone(arr);
  arr2.push(val);
  return arr2;
}

var arr = [];

for (var i = 0; i < 100000; i++) {
  arr = iPush(arr, i);
}